Connectors having various kinds of plastic housings (hereinafter, sometimes referred to simply as "connectors") have conventionally been used for connecting the circuits of electric and electronic instruments or devices for use in motor vehicles. With the recent progress in weight reduction in motor vehicles together with the production of lower-pollution motor vehicles, there is a growing demand for more lightweight connectors. Further, with the increase of the performance and function of motor vehicles, the connectors have come to be required to have a smaller size, more complicated form, improved heat resistance, and improved fitting feeling. The connectors are also required to have improved productivity.
Polybutylene terephthalate (PBT) resins, which are excellent in heat resistance, dimensional stability, and moldability, are used in conventional connectors in large quantities. However, these connectors have had a problem of large weight due to the high specific gravity of the PBT resins. Although 6-nylon resins and 6,6-nylon resins can be advantageously used in the weight reduction of connectors since these resins have lower specific gravities than PBT resins, the nylon resins have had a problem that they have a high water absorption and hence the connectors, upon water absorption, suffer a dimensional change and deterioration in mechanical properties. Thus, 6-nylon and 6,6-nylon resins are not suitable for use in the miniaturization, complication in form, and improvement in fitting feeling of connectors.
In addition to those resins, polypropylene (PP) resins, polyphenylene ether (PPE) resins, ABS resins, and other resins have also been used. Such resins, however, unsatisfactory because they are inferior in heat resistance, chemical resistance, fluidity, etc.
Although attempts are being made to reduce the weight of the connectors employing these resins by foaming, incorporation of a hollow filler or other means, such techniques have been defective in, for example, that the molding accuracy is insufficient and the deterioration of the mechanical properties is severe.